1. Field of the Invention
The present invention relates to an ink-jet recording process. More particularly, it is concerned with an ink-jet recording process for obtaining a color image of high image quality with a high recording density, using plural inks with different hues.
2. Related Background Art
In ink-jet recording processes, recording is carried out by forming ink droplets according to various ink-ejection methods exemplified by the electrostatic attraction method, a method of mechanical vibration or displacement by use of a piezoelectric element, a method of using pressure generated by heating and foaming ink and so forth; and expelling the droplets so that some or all of them adhere on a recording medium such as paper. These are noted as recording methods that can perform high-speed printing and multi-color printing with minimal noise generation.
As the inks for ink-jet recording, those chiefly comprising water are used in view of safety and recording performance, and polyhydric alcohols are often added thereto to prevent nozzle clogging and improve ejection stability.
In instances in which color images are formed by using the ink-jet systems and inks as mentioned above, generally used are cyan (C), magenta (M), yellow (Y) and/or black (Bk) inks to produce each corresponding monochrome at given positions on the recording medium. When neutral tints (mixed colors) thereof are produced, plural ink droplets having different hues are applied in superposition or on mutually overlapping sites on the recording medium.
On the other hand, to obtain shades of recorded images, it is generally practiced to control the application density (an areal gradation method).
The recording medium used for forming color images thereon by the above ink-jet systems include ordinary paper such as wood free and bond paper, coated paper comprising a support having a porous ink-absorptive layer typified by ink-jet paper (Japanese Patent Laid-open Publication No. 214989/1985), etc.
Since the images recorded with these recording media are viewed from the ink-applying surface (the surface on which inks are applied), they are constructed so that as much recording agents remain on such surface as possible, thus having the disadvantage that the durability such as water resistance and abrasion resistance and storage stability of images are inferior and the disadvantage that a recorded image cannot have satisfactory gloss.
A measure to solve such problems is a recording medium disclosed, for example, in Japanese Patent Laid-open Publication No. 136480/1983 and Japanese Patent Laid-open Publication No. 136481/1983. This recording medium comprises a support provided thereon with an ink-receiving layer chiefly comprised of a pigment having a refractive index of 1.58 or less, where the images formed are viewed from the support side. In this method, difficulties in the various performances such as water resistance at the image-viewing surface (the surface from which images are viewed) are sufficiently resolved. However, since the ink-receiving layer is chiefly comprised of the pigment and is contiguously laminated on a transparent support, a large part of the inks which reach to the support is veiled by the pigment even when the pigment has a refractive index of 1.58 or less) making it impossible to sufficiently enhance the image density at the image-viewing surface.
Recently, for higher speed and higher grade recording using ink-jet recording apparatus, recording media also are required to have highly improved recording performances.
More specifically, recording mediums are now to the demanded which have superior to the recording performances such as ink absorbing property, color-developing property for dyes, light-resistance of recorded images, resolution, color performance, recorded image density, storage stability, and gloss.
The present inventors have investigated in order to provide such recording mediums as stated above, and, as a result, have ever proposed a recording medium having a specific constitution such that it comprises a liquid-permeable ink-transporting layer and an ink-retaining layer wherein the ink-applying surface and the image-viewing surface are in an obverse and reverse relationship (EP 227 245 A2).
However, in attempting to obtain color images having a high recording density by using the above recording medium color was insufficiently formed because of the small quantity of ink droplets applied at the monochrome producing areas, resulting in color-forming performances being non-uniform at the neutral tint producing areas.
More specifically, to form a color image using plural kinds of inks of different hues, as many as four droplets may be applied in superposition on one site to develop a neutral tint, while only one ink droplet is applied to develop a unicolor tone. When the number of the ink droplets to be applied varies at every site like this, the ink penetration through the ink-transporting layer also varies depending on the number of the ink droplets, so that the quantity of ink penetrating to the ink-retaining layer to produce an image varies. Moreover, since the ink droplets ejected from an ink-jet nozzle at one time are stagnate in the ink-transporting layer (particularly at the unicolored producing area and therefore little ink may reach the ink-retaining layer. This causes the problems such that there can not be obtained images with uniform color-forming performance, high density and high resolution.